docs: def get_symbol_id_map(self):
          """
          A convenience method to create a mapping between the HGNC
          symbols and their identifiers.
          :return:
  
          """
  
          symbol_id_map = {}
          f = '/'.join((self.rawdir, self.files['genes']['file']))
          with open(f, 'r', encoding="utf8") as csvfile:
              filereader = csv.reader(csvfile, delimiter='\t', quotechar='\"')
              for row in filereader:
                  (hgnc_id, symbol, name, locus_group, locus_type, status,
                   location, location_sortable, alias_symbol, alias_name,
                   prev_symbol, prev_name, gene_family, gene_family_id,
                   date_approved_reserved, date_symbol_changed,
                   date_name_changed, date_modified, entrez_id, ensembl_gene_id,
                   vega_id, ucsc_id, ena, refseq_accession, ccds_id, uniprot_ids,
                   pubmed_id, mgd_id, rgd_id, lsdb, cosmic, omim_id, mirbase,
                   homeodb, snornabase, bioparadigms_slc, orphanet,
                   pseudogene_org, horde_id, merops, imgt, iuphar,
                   kznf_gene_catalog, mamit_trnadb, cd, lncrnadb, enzyme_id,
                   intermediate_filament_db) = row
  
                  symbol_id_map[symbol.strip()] = hgnc_id
  
          return symbol_id_map